Hermetic packages with laser scored vent systems

ABSTRACT

A hermetically sealed package, for example a freezable microwavable package containing a food product, has a sealing film that includes a vent system that is scored by a laser into the package.

BACKGROUND OF THE INVENTION

The present technology generally relates to venting systems for use withfilms that are suitable for use as, or with, food packaging. Morespecifically, the present technology relates to food packaging thatincludes, in certain embodiments, a freezable, microwaveable film layerhaving a venting system that facilitates the heating or cooking ofhermetically packaged food contents at desirable temperatures and/orpressures.

In recent years, there has been an increase in the number of foodproducts that are designed or intended to go directly from the freezerto the microwave for heating or cooking. Such food products oftenrequire packaging that also can go directly from freezer storagetemperatures, typically temperatures ranging from about −20° C. to about0° C., to microwave heating or cooking temperatures ranging from about71° C. or greater. Additionally, it is desirable that such packagingperform without fracturing in the freezer, and without melting orbursting in the microwave. For example, with respect to foods such asvegetables, the temperatures reached during microwave cooking typicallyrange from about 71° C. to about 105° C. However, when the packaged fooditems include meats, fish, grease, and/or oils, for example, thetemperature of the items can reach up to about 150° C. when heatedduring microwave preparation.

Many freezable and microwaveable food packages can be made from, orinclude, a sealing film, such as the multilayered films discussed anddisclosed in U.S. patent application Ser. Nos. 11/374,893 and11/650,903, both of which are incorporated herein by reference in theirentirety. Further, such films may be used for a variety of differenttypes of food packages, which may have a variety of sizes andconfigurations. For example, a sealing film may be configured to form apouch, wherein the sealing film is oriented to provide an inner regionthat is configured to receive the placement of a food product. Further,the edges of the sealing film may be sealed together so that the foodproduct in the inner region is hermetically sealed. Other food packagesmay include a tray container having a base and sidewalls that form theinner region. The inner region of the tray container may also includeone or more food compartments that receive the placement of foodproducts. Often, the inner region of the tray container is covered byattaching a freezable, microwaveable sealing film to the top of thesidewalls or to a flange area so that the food product contained thereinis hermetically sealed.

To ensure proper cooking of the food product in the microwave, and toprevent the food package from bursting, many existing freezable,microwaveable food packages require the inclusion of a vent for thecooking or heating cycle. More specifically, a vent may be added to thesealing film so as to release heat and/or steam that may be generatedwhile cooking or heating the food product in the microwave.

Some freezable, microwaveable food packages do not include a steam ventsystem, but instead rely on the user to create the vent by piercing aslot or hole into the sealing film prior to placing the food packageinto the microwave.

Other types of freezable, microwaveable food packages include built-insteam venting systems. For example, a food package may have built-inholes or slits on the sides or end seals of the sealing film that may beformed by mechanical apparatuses, such as cutters or punches.Additionally, some food packages may have vent systems in the form ofmicro-perforated zones or strips in the sealing film. In some instances,such slits or openings may be formed in a portion of a food package andis subsequently covered or closed by the addition of a laminate to thefood package.

Some freezable, microwaveable food packages provide a built-in vent byscoring a line across most, if not all, the length of the sealing filmof the food package to create a line where the film may tear during thecooking operation. For example, some food packages may use anapproximately 6 inch (15 cm) long scored line across nearly the entirelength of a freezable, microwaveable food package that is in the form ofa pouch. Moreover, this scored line may extend from approximately oneseam or edge to the opposite seam or edge of the package.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a heatable package that includesan inner region, which is configured to receive a product, and a sealingfilm. “Product” is broadly defined here to include any material that cangenerate pressure when heated, either by an external source or by aninternal change of conditions.

The sealing film is comprised of at least one layer of a microwavablefilm that is adapted for use in heating a product, and includes an outersurface and an inner surface. According to some embodiments, the sealingfilm may be a freezable/microwaveable sealing film. The inner region ofthe package may be hermetically sealed by at least a portion of thesealing film. At least one vent pattern is scored by a laser into aportion of the outer surface of the sealing film to form at least oneweakened wall pattern. The vent pattern is scored in the sealing film ata depth that does not perforate the sealing film. Further, the innersurface adjacent to the weakened wall pattern is directly exposed topressure generated in the inner region.

Another aspect of the invention is a heatable package having amulti-layered sealing film that has an inner surface and an outersurface, and which is configured to cover the inner portion of thepackage that contains a product. The inner portion also includes aninner portion span. A vent system comprised of a linear or non-linearvent pattern scored by a laser into the outer surface of themulti-layered sealing film at a depth that does not perforate thesealing film, and which creates a weakened wall pattern. The weakenedwall pattern extends down to at least an adjacent portion of the innersurface. According to certain embodiments, the vent pattern has a ventpattern span that may be from 1% to 100%. According to otherembodiments, the vent pattern has a vent pattern that is a fraction ofthe size of the inner region span, such as, for example, a vent patternthat is 1% to 50% the size of the inner region span. Further, the innersurface of the sealing film that is adjacent to the weakened wallpattern is directly exposed to pressure generated inside the innerregion during heating.

Another aspect of the invention is a method for providing a vent systemin a heatable package that includes scoring at least one linear ornon-linear vent pattern into a sealing film of a package with a laser toform a weakened wall pattern. The vent pattern may have a weakened wallthickness of approximately 5 μm to approximately 25 μm, and may bescored into the sealing film at a depth that does not perforate thesealing film. The vent pattern also has a vent pattern span, which isthe greater of the maximum length and width of the vent pattern.

This aspect of the method further includes sealing at least a portion ofthe sealing film to form a pouch that has an inner surface and an innerregion. The inner region of the pouch is configured to receive aproduct. At least a portion of the inner surface of the sealing film isadjacent to the weakened wall portion.

This aspect of the method also includes sealing the inner region of thepouch to hermetically seal a product contained therein. The sealed innerregion has an inner region span that is equal to the greater of themaximum length and width of the inner region. Additionally, each ventpattern has a vent pattern span that is from 2% to 15% of the size ofthe inner region span.

The method also includes generating a pressure in the inner regionduring heating, wherein the inner surface of the sealing film that isadjacent to the weakened wall portion is directly exposed to thegenerated pressure.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a sealing film for use with a ventsystem according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a portion of a steam vent systemhaving a scored vent pattern and the resulting weakened wall patternacross a portion of a sealing film according to an embodiment of thepresent invention.

FIG. 3 is a perspective view of a freezable, microwaveable pouch-shapedfood package having vent patterns in the form of circles according to anembodiment of the present invention.

FIG. 4 is a perspective view of a freezable, microwaveable pouch-shapedfood package having vent patterns in the form of crosses according to anembodiment of the present invention.

FIG. 5 is a sectional view taken along section line 5-5 of FIG. 3 of apartially expanded freezable, microwaveable pouch-shaped food packagehaving an opened vent according to an embodiment of the presentinvention.

FIG. 6 is a perspective view of a food package in the form of afreezable, microwaveable tray container covered by a sealing film havinga vent system according to an embodiment of the present invention.

The foregoing summary, as well as the following detailed description ofcertain embodiments of the present invention, will be better understoodwhen read in conjunction with the appended drawings. For the purpose ofillustrating the invention, certain embodiments are shown in thedrawings. It should be understood, however, that the present inventionis not limited to the arrangements and instrumentalities shown in theattached drawings or identified in this specification.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a cross-sectional view of a sealing film 100 for use with avent system according to an embodiment of the present invention. Thesealing film 100 may have at least two layers, for example a core layer104 positioned adjacent to an inner, heat sealable layer 102. In theembodiment illustrated in FIG. 1, the sealing film 100 may also includean outer skin layer 106 positioned adjacent to the core layer 104.Further, an outer protective layer 110 may be adhered, such as throughthe use of an adhesive 108, to the outer skin layer 106.

Each layer of the sealing film 100 may be constructed from a variety ofdifferent base materials. For example, each layer of film in the sealingfilm 100 may be made from the same or different base materials,including a thermoplastic polymer, polyolefin, polyethylene,polypropylene, propylene/ethylene copolymer, or propylene/alpha-olefincopolymer, along with derivatives thereof, among others. Examples of theadhesive 108 include, but are not limited to, polyurethane, epoxides,hot-melt ethylene vinyl acetate, hot melt polyamide, and hot-meltpolyester. Further, the sealing film 100 may be manufactured using avariety of film processing techniques, for example by lamination andcoextrusion, including blown film coextrusion and a cast film process,among others. Further, the thickness of the sealing film 100 may depend,at least in part, on the size of the food package to be made from, or toinclude, the film 100. For example, according to certain embodiments,the sealing film 100 may have a thickness from about 2 mils to about 5mils (50 to about 130 microns). The sealing film 100 optionally can beconstructed to withstand freezing, followed by heating to a cooking orother processing temperature.

FIG. 2 is a cross-sectional view of a portion of a steam vent system 202having a scored vent pattern 204 and the resulting weakened wall pattern114 across a portion of a sealing film 100 according to an embodiment ofthe present invention. As shown in FIG. 2, the sealing film 100 may havean outer surface 116 and an inner surface 118.

According to certain embodiments, the vent pattern 204 may be created bya laser beam scoring at least one vent pattern 204 into the outersurface 116 of the sealing film 100. For example, the vent pattern 204may be scored into the sealing film 100 using an approximately 10.2 μmor 10.6 μm wavelength CO₂ laser operated at about 20 watts to 200 watts.The laser can be scanned or otherwise moved related to the film 100, orvice versa, for example at 70 ft/min (0.36 m/sec). The vent pattern 204can be scored into the sealing film 100 at a depth that does notperforate the sealing film 100. By not perforating the sealing film 100,the scored vent pattern 204 may allow the package 200 to be hermeticallysealed, and thereby prevent or resist microorganisms or oxygen fromentering into the package 200 through the vent pattern 204 that couldcontaminate or degrade the product contained therein. Further, the lackof perforations in the scored vent pattern 204 may prevent productcontained within the package 200 from leaking out of the package 200through the vent pattern 204.

Mechanically formed vent systems, such as those that cut, slit, orpierce the sealing film, typically rely on a subsequent laminationmanufacturing step to cover openings in the sealing film created by suchoperations. In such operates, laminate is subsequently applied in anattempt to create a package that may be hermetically sealed. However,the use of a laser to score the package may remove the need for such alamination procedure. More specifically, the laser, such as theapproximately 10.2 μm or 10.6 μm wavelength CO₂ laser described above,may be operated to score the sealing film without cutting or piercingthrough the wall of the sealing film. And because such a laser may beoperated so as to not create such openings, the sealing film may stillbe suitable for use in a hermetically sealed package without the needfor the subsequent lamination procedure that may be associated withcovering holes in mechanically formed vent systems.

The vent pattern 204 can define a weakened wall pattern 114 in thesealing film 100. For example, according to embodiments in which thesealing film 100 is a 3.5 mil (89 micron) laminate, the vent pattern 204may be scored into the sealing film 100 to create a weakened wallpattern 114 that has a wall thickness of approximately 5 μm toapproximately 25 μm.

FIGS. 3 and 4 are perspective views of a freezable, microwaveablepouch-shaped food package 200 having a vent system 202 comprising ventpatterns 204, 206 in the form of circles and crosses, respectively,according to embodiments of the present invention. The food package 200may be manufactured using conventional packaging equipment. For example,according to embodiments in which the food package 200 is a pouch,vertical form fill and seal equipment or horizontal form fill and sealequipment may be used to form the food package 200. Typically, in theoperation of such equipment, the sealing film 100 that is to be formedinto the food package 200 is fed from a roll to the equipment where itis wrapped about a forming tube and a longitudinal heat seal is providedto form the fin seal 207, closing the sealing film 100 to form a tube.Thereafter, one end of the tube is closed and inner heat seal layers areheat sealed together to form one end of an inner region, which is thenfilled with a predetermined quantity of product. The filled food package200 is then closed and the inner heat seal layers are heat sealedtogether at the open end to form a food product packaged in ahermetically sealed food package 200. As shown in FIGS. 3 and 4, thefood package 200 may include end seals 205 a, 205 b, and a fin seal 207.

One can use a single scored line, which can be straight, curved, or aclosed loop, to create a weakened wall pattern 114 forming the ventsystem 202. Alternatively, one can utilize two or more vent patternssuch as 204, 206 that are scored into the outer surface 116 of thesealing film 100 by a laser or other means. For example, FIGS. 3 and 4illustrate food packages 200 having a vent system 202 comprising atleast one vent pattern, and have two vent patterns 204 or 206 perpackage, in the form of a circle or a cross, respectively. However, avariety of different shapes and patterns may be used to form the ventpatterns 204, 206, for example closed loop patterns, such as atrapezoid, rectangle, square, triangle, oval, circle, as well as othernon-linear patterns, such as crosses, “I”-shaped patterns, and“T”-shaped patterns, along with combinations and variations thereof,among others.

By using a vent pattern having short dimensions, rather than a singlelong scored line, the size of the vent created by separation along thepattern may be controlled. For example, if a long scored line is used,the entire line may open, whereby the pressure in the food package maydrop to an atmospheric level that prevents the food product from beingcooked uniformly to a desired temperature, and which may then result ininsufficient cooking or heating or cold spots in the cooked or heatedfood or other product. Alternatively, the scored line may not open,which may cause the food package to burst or delaminate, or causecontents to leak out of the seal. Another possible result is loss of thehot food product from the food package, which presents a safety hazardfor the user.

The amount of steam generated during the heating or cooking of aproduct, and thus the amount of pressure needed to be released from thepackage 200 in order to maintain desired pressures and temperatureswithout bursting the package 200, depends on a variety of factors. Forexample, if the product to be heated or cooked is a frozen food product,the vent system 202 may be designed with considerations given to suchfactors, such as the food type, moisture content, the size and weight offood package 200, and anticipated microwave power, among other factors.Moreover, in such instances, the vent system 202 may be configured toallow for a heating or steam pressure of 0.25 to 2.0 psi to bemaintained within the package 200 so that the food product containedtherein may be uniformly heated or cooked at a desired temperature, suchas above 160° F.

The vent pattern such as 204, 206 may be sized to accommodate thevarious types and weights of food products that are packaged within thefood package 200. For example, for a 12 ounce (340 g) frozen foodproduct that is contained in an approximately 6.5 inch (17 cm) wide by 9inch (23 cm) long food package 200, the vent system 202 may include twocircular vent patterns 204 having a diameter of approximately 4 mm to 20mm, or include two vent patterns 206 in the shape of crosses, wherein atleast one and optionally both of the intersecting lines of the cross hasa length of 4 mm to 20 mm.

The vent pattern 204, 206 can have a line thickness and/or depth thatallows for the formation of the weakened wall pattern 114, while stillallowing a hermetic seal to be formed and/or maintained about thepackaged food product. Further, the line thickness and/or depth of thevent pattern 204, 206 can be such as to prevent the food package 200from opening along at the weakened wall pattern 114 prior to, or tooearly during, the cooking or heating of the food package. Additionally,the line thickness and/or depth of the vent pattern 204, 206 can besized to be large enough to allow at least a portion of the weakenedwall pattern 114 to open during cooking or heating, as necessary so thatundesirable excess pressure may be released from within the food package200, but small enough to allow a desired pressure level to be maintainedinside the food package 200. This can be accomplished, for example, bysizing the vent pattern 204, relative to the desired heating conditions,so the pattern 204 opens to create a vent when the desired triggeringpressure is generated in the package 200, and so steam or other vapor atthe desired pressure is released through the vent at about the same rateas additional steam is formed.

According to certain embodiments, the vent pattern 204, 206 may have awall thickness of approximately 5 μm to approximately 25 μm. Such a wallthickness for the vent patterns 204, 206 may also facilitate thegeneration of micro-voids or cracks in the weakened wall pattern 114 asthe sealing film is expanded during heating.

FIG. 5 is a sectional view taken along section line 5-5 of FIG. 3 of apartially expanded freezable, microwaveable pouch-shaped food package200 having opened vents 201 a, 201 b according to an embodiment of thepresent invention. As shown in FIG. 5, the sealing film 100 may beoriented so that the food package 200 may include a first wall 220 and asecond wall 222. The food package 200 may be placed within the microwavewith the outer surface 116 b of the second wall 222 facing in agenerally upward direction. Accordingly, the food product 300 may in theinner region 120 against at least a portion of the inner surface 118 aof the first sidewall 220.

As previously mentioned, the vent patterns 204 a, 204 b may be scoredinto the sealing film 100 at a depth that does not puncture the sealingfilm 100. Further, because no secondary seals or other connections orattachments within or along the food package 200 shields the weakenedwall pattern 114 from the pressure generated in the inner region 120during heating, the weakened wall pattern 114 is able to expand with therest of the sealing film 200 during the cooking or heating cycle.Accordingly, the weakened wall pattern 114 may remain closed until thepressure within the inner region 120 of the food package 200 causes thesealing film 100 to expand to a size that tears or cracks at least aportion of the weakened wall pattern 114, and thereby opens at least aportion of one or more of the vents 201 a, 201 b. At least initially,this tearing may take the form of micro-voids or cracks along at least aportion of the weakened wall pattern 114, through which excess pressuremay be released from the inner region of the food package. However, ifthe pressure level within the inner region 120 continues to rise, andthe sealing film 100 continues to expand, the size and/or number of thecracks and micro-voids along the weakened wall pattern 114 may increase,thereby reducing the pressure in the inner region 120.

In some instances, the sealing film 100 may continue to expand until thesize or number of micro-voids and/or cracks results in larger tears inat least sections of the weakened wall pattern 114. However, the size ofthe tear in the weakened wall pattern 114 is controlled, or limited, bythe size of the vent pattern 204 a, 204 b. For example, in theembodiment illustrated in FIG. 5, if the vent pattern 202 a is a circlehaving an approximately 12 mm diameter, the largest vent 201 a createdby the tearing or separation along the weakened wall pattern 114 isgenerally circular in shape and has an approximately 12 mm diameter. Bycontrolling or limiting the maximum size of the vent 201 a generatedabout the weakened wall pattern 114, the amount of pressure releasedthrough the vent(s) 201 a, 201 b is controlled, which allows thepressure and/or temperature within the inner region 120 to be maintainedat a desirable level for heating.

FIG. 6 is a perspective view of a food package 300 in the form of afreezable, microwaveable tray container 302 covered by a sealing film100 having a vent system 202 according to an embodiment of the presentinvention. The tray container 302 may have a variety of differentshapes, including rectangular, square, circular, oval, trapezoidal, andtriangular, among others.

The tray container 302 illustrated in FIG. 6 has a generally oval shape.The tray container 302 may include sidewalls 306 that define a recessedinner region 308. The inner region 308 may be comprised of at least onefood compartment 310, 312 that is configured to receive a food product.The inner region 308 may be covered by a sealing film 100 that isattached to a top portion 311 of the tray container 302. For example, inthe embodiment illustrated in FIG. 6, an upper flange area 314 may beconnected to, or part of, the sidewalls 308, and may provide a surfacefor attaching or sealing the sealing film 100 to the tray container 302.The sealing film 100 may be used in combination with the tray container302 to hermetically seal the food product contained in the inner region308.

The vent system 202 used with a food package 300 having a tray container300 may be similar to that previously discussed above for thepouch-shaped food package 200. Moreover, the vent system 202 may includeat least one vent pattern 206 that has been scored into the sealing film100 to create a weakened wall pattern 114. For example, as shown in FIG.6, the vent system 202 may include two vent patterns that are eachcross-shaped.

Further, each vent pattern 204, 206 has a vent pattern span, which isthe larger of the maximum width and length of the vent pattern 204, 206.The inner region 120, 308 has an inner region span, which is the largerof the maximum width and length of the inner region 120, 308. Forexample, if the maximum length of the inner region 120, 308 of thepouch-shaped or tray-container food package 200, 300, as labeled inFIGS. 4 and 6 as “l₁”, is 9 inches, and the maximum width of the innerregion 120, 308 of 6.5 inches (17 cm), as labeled “w₁”, than the size ofthe inner region span is the maximum length, i.e. 9 inches (23 cm).Conversely, if the maximum width is 9 inches (23 cm), and the maximumlength is 6.5 (17 cm), than the size of the inner region span is equalto the maximum width, i.e. 9 inches (23 cm). However, if the maximumwidth and length of the inner region 120, 308 are equal, than either maybe used for purposes of determining the size of the inner region span.Similarly, if the maximum length and width of the vent pattern 204, 206are equal (as indicated in FIG. 4 as “l₂” and “w₂” respectively), thaneither size may be used for purposes of determining the size of the ventpattern span.

The vent pattern span for each vent pattern 204, 206 of the presentinvention may be sized to be a fraction of the inner region span. Forexample, according to certain embodiments, if the inner region span is 9inches (23 cm), and each vent pattern has an individual vent patternspan of 12 mm, such as a vent pattern 204 being a circle having adiameter of 12 mm, or a cross shaped vent pattern 206 comprised of twointersecting lines, the longest, or both lines, having a length of 12mm, vent pattern span is approximately 5% of the size of the innerregion span. However, the difference between the size of the innerregion span and the vent pattern span may depend on a number ofdifferent factors, including the type of food product being packaged andthe size of the food package 200, 300. For example, according to certainembodiments of the present invention, each individual vent pattern spanmay be from 1% to 100% of the size of the inner region span. Accordingto some embodiments, each vent pattern may have a vent pattern span thatis from 1% to 50% of the size of the inner region span. According toother embodiments, each vent pattern may have a vent pattern span thatis from 2% to 15% of the size of the inner region span. According toother embodiments, each vent pattern may have a vent pattern span thatis from 4% to 8% of the size of the inner region span. Further, the ventsystem 202, 304 of the present invention may have more than one ventpattern 204, 206, and each vent pattern may have the same or a differentvent pattern span.

EXAMPLE 1 Pouch-Shaped Food Package Having Circular Vent ScoringPatterns

An approximately 6.5 inch (17 cm) wide by 9 inch (23 cm) long foodpackage was formed in the shape of a pouch using Pliant'sfreezable/microwaveable Steam Quick™ laminate. The food package includedtwo end seals, each having a width of approximately 0.4 cm toapproximately 1.2 cm, which allowed for an inner region span ofapproximately 14.6 cm to approximately 16.2 cm. The food packageincluded two vent scoring patterns in the form of circles havingapproximately 12 mm diameters. The vent patterns were scored into thelaminate with the use of a 10.2 μm wavelength CO₂ laser at about 40watts of power and scanned at about 70 ft/min (0.36 m/sec), and did notperforate the laminate. The inner region of the pouch was filled with 12ounce (340 g) of frozen broccoli cuts and manually hand sealed by a heatsealer. The food package was then stored in a freezer for 24 hours at−5° F. (−21° C.).

Upon removing the food package from the freezer, the food package wasplaced in a microwave, and underwent 6 minutes of cook time atapproximately 1200 watts of power. One pressure probe and fourtemperature probes were inserted into the pouch before, during, andafter the cook cycle. The food package was also observed expandingduring the cook cycle, along with the weakened wall along the two scoredvent patterns opening accordingly to release heat and steam during thecook cycle. The maximum pressure detected by the pressure probe in themicrowave testing was 0.98 psi (0.07 bar). The maximum temperaturereached was 229.4° F. (110 ° C.). The food temperature was 193.5° F. (90° C.). The food was also observed to have been cooked uniformly.

EXAMPLE 2 Pouch-Shaped Food Package Having Cross Vent Scoring Patterns

An approximately 6.5 inch (17 cm) wide by 9 inch (23 cm) long foodpackage was formed in the shape of a pouch using Pliant'sfreezable/microwaveable Steam Quick™ laminate. The food package includedtwo end seals, each having a width of approximately 0.4 cm toapproximately 1.2 cm, which allowed for an inner region span ofapproximately 14.6 cm to approximately 16.2 cm. The food packageincluded two vent scoring patterns in the form of crosses, with thelength of each line in the cross being approximately 12 mm long. Thevent patterns were scored into the laminate with the use of a 10.2 μmwavelength CO₂ laser at about 40 watts of power and scanned at about 70ft/min (0.36 m/sec), and did not perforate the laminate. The innerregion of the pouch was filled with 12 ounce (340 g) of frozen broccolicuts and manually hand sealed by a heat sealer. The food package wasthen stored in a freezer for 24 hours at −5° F. (−21 ° C.).

Upon removing the food package from the freezer, the food package wasplaced in a microwave, and underwent 6 minutes of cook time atapproximately 1200 watts of power. One pressure probe and fourtemperature probes were inserted into the pouch before, during, andafter the cook cycle. The food package was also observed expandingduring the cook cycle, along with the weakened wall along the two scoredvent patterns opening accordingly to release heat and steam during thecook cycle. The maximum pressure detected by the pressure probe in themicrowave testing was 1.3 psi (0.09 bar). The maximum temperaturereached was 219.4° F. (104° C.). The food temperature measured was192.3° F. (89° C.). The food was also observed to have been cookeduniformly.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Therefore, it is intended that the invention not be limited to theparticular embodiment disclosed, but that the invention will include allembodiments falling within the scope of the appended claims. Further, atleast some of the numerical ranges stated above are not necessarilycritical.

1. A heatable package comprising: an inner region configured to receivea product; a sealing film, the sealing film being comprised of at leastone layer of a microwavable film adapted for use in heating the product,the sealing film having an outer surface and an inner surface, the innerregion of a heatable package being hermetically sealed by at least aportion of the sealing film; and at least one weakened wall patternscored by a laser into a portion of the outer surface of the sealingfilm at a depth that does not perforate the sealing film, the innersurface adjacent to each weakened wall pattern being directly exposed topressure generated in the inner region.
 2. The heatable package of claim1 wherein the inner region has an inner region span that is equal to thegreater of a maximum width and a maximum length of the inner region,each weakened wall pattern has a vent pattern span that is the greaterof the maximum length and the maximum width each pattern, and whereineach weakened wall pattern has the vent pattern span that is from 1% to50% of the size of the inner region span.
 3. The heatable package ofclaim 2 wherein each weakened wall pattern has a non-linearconfiguration and the vent pattern span is from 2% to 15% of the innerregion span.
 4. The heatable package of claim 2 wherein the vent patternspan is from 4% to 10% of the inner region span.
 5. The heatable packageof claim 1 wherein the wall thickness of the weakened wall pattern is 5μm to approximately 25 μm.
 6. The heatable package of claim 1 whereinthe at least one weakened wall pattern is a closed loop.
 7. The heatablepackage of claim 1 wherein the at least one weakened wall pattern has agenerally circular shape with a diameter of about 4 mm to 20 mm.
 8. Theheatable package of claim 1 wherein the at least one weakened wallpattern has a wall thickness this is from 5 μm to 25 μm.
 9. The heatablepackage of claim 1 wherein the at least one weakened wall pattern is across that is comprised of at least one intersecting line having alength of about 4 mm to 20 mm.
 10. The heatable package of claim 1wherein the laser is an approximately 10.2 μm wavelength CO₂ laser. 11.The heatable package of claim 1 wherein the laser is an approximately10.6 μm wavelength CO₂ laser.
 12. The heatable package of claim 1wherein the heatable package has a pouch configuration.
 13. The heatablepackage of claim 1 further comprising a tray container, at least aportion of the sealing film being attached to the tray container tohermetically seal the product inserted into the inner region.
 14. Aheatable package comprising: a multi-layered sealing film having aninner surface and an outer surface and configured to cover an innerregion of the heatable package, the inner region being configured tocontain a product and have an inner region span; a vent systemcomprising a non-linear vent pattern scored into the outer surface ofthe multi-layered sealing film to create a weakened wall pattern at adepth that does not perforate the multi-layered sealing film, theweakened wall pattern extending down to at least an adjacent portion ofthe inner surface and having a vent pattern span, the vent pattern spanbeing from 1% to 50% of the size of the inner region span, and the innersurface adjacent to the weakened wall pattern being directly exposed topressure generated inside the inner region during heating.
 15. Theheatable package of claim 14 wherein the non-linear vent pattern isscored by a laser to have a line thickness of 5 μm to 25 μm.
 16. Theheatable package of claim 14 wherein a wall thickness of the weakenedwall pattern is 5 μm to approximately 25 μm.
 17. The heatable package ofclaim 14 wherein the vent pattern span is from 4% to 8% of the innerregion span.
 18. The heatable package of claim 14 wherein each ventpattern is a closed loop.
 19. The heatable package of claim 14 whereineach vent pattern is a cross.
 20. The heatable package of claim 14wherein the non-linear vent pattern is scored into the multi-layeredsealing film using an approximately 10.2 μm wavelength CO₂ laser. 21.The heatable package of claim 14 wherein the non-linear vent pattern isscored into the multi-layered sealing film using an approximately 10.6μm wavelength CO₂ laser.
 22. A method for providing a vent system in aheatable package, the method comprising the steps of: scoring at leastone non-linear vent pattern into a sealing film with a laser at a depththat does not perforate the sealing film to form a weakened wallpattern, the at least one non-linear vent pattern having a wallthickness of approximately 5 μm to approximately 25 μm, and each ventpattern having a vent pattern span that is greater than both a lengthand a width of each vent pattern; sealing at least a portion of thesealing film to form a pouch, the pouch having an inner surface definingan inner region that is configured to receive a product therein, atleast a portion of the inner surface being adjacent to the weakened wallpattern; sealing the inner region of the pouch to hermetically seal theproduct contained in the inner region, the inner region having an innerregion span that is equal to the greater of a maximum length and amaximum width of the inner region, wherein the vent pattern span is from2% to 15% of the inner region span; and generating a pressure in theinner region during heating, the inner surface adjacent to the weakenedwall pattern being directly exposed to the pressure.
 23. The method ofclaim 22 wherein the vent pattern span is 4% to 8% of the inner regionspan.
 24. The heatable package of claim 22 wherein the scoring isperformed using an approximately 10.2 μm wavelength CO₂ laser.
 25. Theheatable package of claim 22 wherein the scoring is performed using anapproximately 10.6 μm wavelength CO₂ laser.